Barack Obama delivered the most impassioned speech of his presidency on Sunday night, addressing the grieving families of Newtown, Connecticut with words of comfort while delivering a clarion call to the nation that enough was enough and that the "carnage" of mass shootings must end.

White House observers had expected the president to give an emotional address that would skirt around difficult issues relating to the country's bloody marriage to firearms. But in the end in a speech that did not include a single reference to the word "gun", he issued the strongest cry for change in gun policy of any political leader in a generation.

Addressing an audience of about 900 local people, including about 15 families of victims, at Newtown high school he talked about the disaster at Sandy Hook elementary school, in which "20 beautiful children and six remarkable adults" had died. He said since the terrible events he had been reflecting on a simple question: was America meeting "our first task, our first job: caring for our children. If we don't get that right we don't get anything right."

He answered his own question with a blunt answer that will prick up the ears of Congress and set alarm bells ringing at the offices of the National Rifle Association, arguably the country's most powerful lobbying group that, though it received no mention either, was palpably the elephant in the room. "The answer," Obama said, "is no."

Looking sombre and at times worn, Obama talked about the burden he has had to carry, as all modern US presidents do, of comforting the survivors of mass shootings and consoling the families of victims. This was no fewer than Obama's fourth such agonising trip to a town held in the grip of unfathomable mourning, an average of one for every year of his first term.

He travelled to Fort Hood, Texas soon after the 5 November 2009 tragedy in which 13 service members died at the hands of a fellow military member; he was in Tucson, Arizona days after the 8 January 2011 that left the Congress member Gabby Giffords shot in the head and six dead; and he was in Aurora, Colorado to mark the 20 July rampage in a cinema in which 12 people were killed. Now, less than five months later, he was back in this dark place once again.

And he had a clear message this time, unlike any of his previous responses: "We can't tolerate this any more. These tragedies must end. And to end them, we must change."

Without straying into specifics, he laid down the parameters of the change that he said America now has to make. He promised to engage law enforcement, parents, educators and others in a dialogue on how to prevent further mass shootings.

"What choice do we have? We cannot accept events like this as routine. Are we really prepared to say we are powerless in the face of such carnage? That the violence visited on our children year after year is the price of our freedom?"

Obama's oratory was not the only poignant point in an exceptional evening. There was the haunting singing by Rabbi Shaul Praver of Congregation Adath Israel of El Maleh Rachamim, the Hebrew prayer for the soul of the departed traditionally chanted at a funeral.

There was the reading of Psalm 23 by the Episcopal pastor Kathleen Adams-Shephard: "Though I walk through the valley of the shadow of death, I will fear no evil." And there was the address by the First Selectwoman of Newtown Patricia Llodra, who described the community as one that "loves children above all."

"It is a defining moment for our town," she said, "but it does not define us. We are defined by acts of courage, by acts of love and our continuing commitment for our children."

But despite all those moments, the most powerful words were Obama's, words that if he has the strength in his second term to follow through on them could spell deep changes ahead for America. "I'll use whatever power I have to prevent the type of tragedy that occurred in Newtown," he said.

And then, to a hushed congregation, he dealt his most powerful card. He read out the names of the 20 children who lost their lives on Friday, slowly, deliberately, stopping occasionally to contain his own emotions.

"God has called them all home," he said. "To those of us who remain, let us find the strength to carry on and make our country worthy of their memory."